Acute Promyelocytic Leukemia
Acute promyelocytic leukemia (APL) is a rare cancer affecting the blood and bone marrow. It occurs primarily in middle-aged adults, but it also can affect children.
Prompt diagnosis and treatment reduce symptoms long-term (remission) and often cure APL. The disease may progress rapidly and become life-threatening if treatment doesn’t start right away.
What is acute promyelocytic leukemia?
Immature white blood cells called promyelocytes develop in the bone marrow (soft, spongy middle part of bones). They normally mature to become white blood cells that fight infection.
In APL, uncontrolled growth and storage of promyelocytes occur in the bone marrow. This reduces the bone marrow’s ability to make red blood cells and platelets.
After these abnormal white blood cells build up in the bone marrow, they can spill over into the blood. This allows these cancerous cells to spread to other areas of the body quickly.
Acute promyelocytic leukemia facts and stats
- APL occurs in one in every 250,000 people.
- APL occurs most commonly in adults around age 40 and in children between ages eight to ten.
- APL accounts for 5 to 15% of all acute myeloid leukemia cases.
- APL accounts for 4 to 10% of all acute myeloid leukemia childhood cases.
- Around 85 to 90% of individuals treated for APL achieve complete remission.
- Around 75% of people in remission for APL survive cancer-free for five years.
Causes and risk factors of acute promyelocytic leukemia
Genes store instructions for making molecules that allow human cells to function. Chromosomes are structures in cells that store genes.
Over 95% of acute promyelocytic leukemia cases involve mutations in two genes—the PML gene on chromosome 15 and the RARA gene on chromosome 17. APL is not an inherited condition because these mutations occur after a person’s conception.
The two chromosomes swap genetic material (chromosomal translocation) after pieces of the two genes break off. Parts of these two genes join together in a fusion gene called PML/RARα.
Risk factors for developing APL include:
- Age (risk increases as age increases)
- Hispanic ethnicity
- Occupational exposures such as electromagnetic fields and toxic chemical agents such as benzene
- Previous treatment with chemotherapy or radiation
Signs and symptoms of acute promyelocytic leukemia
- Easy bruising, including small red dots under the skin called petechiae
- Excessive bleeding (especially nosebleeds, gum bleeding, heavy menstrual flow, and blood in urine)
- Frequent infections/fever
- Loss of appetite or weight
- Pain in joints and bones
- Pale skin
Diagnosing acute promyelocytic leukemia
Your doctor gives you a physical exam and reviews your medical history to diagnose APL.
Tests may include:
- Blood tests: These tests determine the number of platelets, white blood cells, and red blood cells in a sample of your blood. Blood tests also allow doctors to assess liver and kidney function and detect signs of inflammation and infection.
- Bone marrow aspiration or biopsy: Your doctor removes a small bone marrow or bone tissue sample for analysis using a thin, hollow needle. Analysis of the sample detects abnormal white blood cells or promyelocytes.
- Clotting tests: These tests measure how quickly your blood can clot after an injury. Doctors determine your risk for bleeding with these tests.
- Imaging: X-rays, magnetic resonance imaging (MRI) scans, or computed tomography (CT) scans may reveal bone abnormalities caused by APL.
- Genetic testing: Genetic tests detect the chromosomal translocation and fusion of the PML and RARA genes. This confirms APL.
Your doctor determines the right treatment for you based on your risk level after gathering all the information. There are two risk levels for APL:
- Low-risk: You are low-risk if your white blood cell count is 10,000 cells per microliter or less.
- High-risk: You are high-risk if your white blood cell count is more than 10,000 cells per microliter.
Treatments acute promyelocytic leukemia
Treatment options for APL include:
- All-trans retinoic acid (ATRA): Doctors initially treat APL using the non-chemo drug ATRA (also called tretinoin). This targeted therapy stops white blood cells from getting stuck in the immature stage by speeding up their maturation.
- Arsenic trioxide: Doctors use this non-chemo drug to treat APL that comes back or does not respond to initial treatments well. It is often combined with ATRA and also works by speeding up white blood cell maturation.
- Chemotherapy: Chemotherapy drugs are medications that are toxic to cancer cells. Chemotherapy works by slowing the rapid growth of cancer cells or killing them. Doctors give chemotherapy in pill form or by injection.
- Clinical trials: Clinical trials take place at specific medical centers. Eligible patients may get access to promising treatments. These treatments often are not widely available yet.
- Stem cell transplantation (bone marrow transplant): Healthy stem cells (blood-forming cells in bone marrow) replace unhealthy stem cells in this procedure. Replacement stem cells may come from a donor or your own (healthy) cells.
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